1. Field of the Invention
The present invention relates to a wave-form observation apparatus.
The invention is particularly concerned with an apparatus for displaying and observing an input picture signal and/or a stored input picture signal simultaneously or individually. The input picture signal includes wave-forms, characters and/or figures with their intensity (i.e. brightness) information for display.
2. Description of the Prior Art
Shown in FIG. 1 is a circuit diagram of a prior art wave-form observation apparatus employed in osciloscopes.
In FIG. 1, there is an input picture signal 1. This is an analog signal including wave-forms, characters and figures with their intensity (i.e. brightness) informations for display. The analog input picture signal 1 is applied to an A/D converter 10, The A/D converter converts the analog input signal 1 to a picture data 2.
A comparator 11 receives the picture data 2 and a subtracted picture data 3 delivered from a subtracter 13. The comparator 11 compares two intensity (i.e. brightness) data included in broth data 2 and 3. When the intensity of the data 2 is stronger than another, the comparator 11 delivers a compared result 4. The compared result 4 is applied to a switch S2. The picture data 2 connected with a terminal "a" of a switch S2 is applied to a memory 12 as a intense picture data 6. The data 6 is stored therein. In this case, the data 6 is the same data as the data 2.
The memory 12 delivers a stored picture data 7 including intensity data to the subtracter 13. Therein, a predetermined subtractive value is subtracted from the intensity data, Thereby, an intensity of the stored picture data 7 decreases. A subtracted picture data 3 including decreased intensity data is obtained from the subtracter 13. The data 3 is connected with the comparator 11 and a terminal "b" of the switch S2.
When the intensity of the subtracted picture data 3 is not smaller than that of data 2 in the input of the comparator 11, the data 3 connected with the terminal "b" of the switch S2 is applied to the memory 12 as a bright picture data 6. The above-mentioned operation is repeated.
A display composer 17 composes the picture data 2 and the
subtracted picture data 3 to apply the composed data to a display 18. Input wave-forms included in the data 2 and/or stored wave-forms included in the data 3 are simultaneously or individually displayed on the display 18 at timing of a display timing signal 8 delivered from a display timing generator 14.
There are shown in FIG. 2 time charts of the intense picture data 6(a) and the display timing signal 8(b).
A display cycle T is a time interval between a timing t1 and t2 or t2 and t3. A picture is displayed on the display 18 and stored in the memory 12 at a display cycle T.
The picture data 2 and the subtracted picture data 3, which is delivered from the intense picture data 6 via the memory 12 and the subtracter 13, are composed by the display composer 17 and displayed on the display 18 every display cycle T.
When the predetermined subtractive value of the subtracter 13 is large, a picture (e.g. wave-forms) with afterglow (i.e. persistent in eyesight) for a short time period is observable on the display 18. When the predetermined subtractive value is small, a picture (e.g. wave-forms) with the afterglow (i.e. persistent in eyesight) for a long time period is observable on the display 18. When the predetermined subtractive value is zero, the afterglow (i.e. persistent bright) for an infinity time period is obtainable because the stored picture data 7 is repeatedly displayed. This is an infinity afterglow operation.
When the predetermined subtractive value is large enough or a writing operation to write the intense picture data 6 into the memory 12 is inhibited wave-forms included in the input picture signal 1 are displayed, on the display 18. This is a non afterglow operation.
When the infinity afterglow operation and the non afterglow operation are alternately repeated, the current wave-forms included in the picture data 2 and the stored past wave-forms included in the subtracted picture data 3 are displayed simultaneously in human eyesight. In case of watching changes of wave-forms in various measurement conditions, the current wave-forms and the stored past wave-forms are simultaneously displayed.
In a multichannel wave-form observation apparatus, the memory 12 has storage segments. Each storage segment is for each channel. In such a case, current wave-forms and past wave-forms of multichannels are simultaneously displayable for comparison observation. In order to display past wave-forms, the infinity afterglow operation and a freezing operation to inhibit the memory 12 from rewriting are required. Those operations are complicated.